Gas turbines are widely used in commercial operations for power generation. Gas turbine combustors generally operate on a liquid and/or a gaseous fuel mixed with a compressed working fluid such as air. The flexibility to run a gas turbine on either fuel provides a great benefit to gas turbine operators.
It is widely known that the thermodynamic efficiency of a gas turbine increases as the operating temperature, namely the combustion gas temperature, increases. It is also known that higher combustion gas temperatures may be attained by providing a rich fuel/air mixture in the combustion zone of a combustor. However, higher combustion temperatures resulting from a rich liquid or gaseous fuel/air mixture significantly increase the generation of nitrogen oxide or NOx, which is an undesirable exhaust emission. NOx levels may be reduced by providing a lean fuel/air ratio for combustion or by injecting additives, such as water, into the combustor.
To provide a lean fuel/air mixture the fuel and air may be premixed prior to combustion. The premixing may take place in a dual-fuel combustor fuel nozzle, which includes multiple fuel injection ports, an inner flow region and an outer flow region. As the gas turbine cycles through various operating modes, fuel is injected into the inner and/or outer flow regions for premixing with the working fluid. A variety of dual-fuel nozzles exist which allow premixing of a liquid and/or gaseous fuel with a working fluid prior to combustion. However, an improved fuel nozzle and method for supplying fuel to a combustor that improves the uniformity of the fuel mixture would be useful.